By obtaining position information using a GPS function included in a mobile terminal and the like, monitoring is performed, for example, where is a user carrying the mobile terminal and the like, with which route the user is moving, or whether the user approaches a restricted area, a hazardous area, and the like or not.
However, GPS information used for obtaining the position has a problem in accuracy, and especially, inside a building or when approaching a high-rise building, the mobile terminal and the like cannot catch a satellite to cause a big error between an actual position and a detected position in some cases.
There has been proposed an idea where correction of the position information is performed to such an error to provide the position information closer to the actual position.
In Patent Literature 1, with a communication controller configured to communicate with a monitoring terminal, when a difference between a calculated position at this time and a current display position is larger than a position detection allowable error, a point closest to the current display position on a circumference of an error distribution circle is determined as an estimated position at this time. When the difference between the calculated position at this time and the current display position is smaller than the position detection allowable error, a point internally dividing between the current display position and the calculated position at this time in a predetermined ratio is determined as the estimated position at this time. Then, between the current display position and the calculated position at this time is further divided into a predetermined number, and smoothly displayed on a screen on the monitoring terminal side at every refresh rate of the screen. This reduces an unnatural screen display due to the position detection error and ensures more natural display of a worker's movement.